Coloration of fresh citrus fruits



Patented Apr. 11, 1950 2,503,665 COLORATION or FRESH CITRUS FRUITS CarlE. Gerlcke, Puerto Castilla, Honduras, alsigner to American MachineryCorporation, Orlando, Fla., a corporation of Florida No Drawing.Application February 2, 1950,

Serial No. 141,871

11 Claims. 1

This invention relates to the commercial preparation of fresh wholefruit for the market, and particularly to the impartation of' adesirable coloration. More in particular this refers to citrus fruitwhich reaches a stage of maturity wherein the fruit itself has come to aripened condition but the skin or peel thereof has an off-color and insome extreme cases a yellow or greenish yellow color, which lowers theiracceptance on the market. This application for Letters Patent is acontinuation-in-part of the copending application, Serial No. 692,701,filed August 23, 1946.

As disclosed in Patent No. 1,909,860, issued to Rodney B. Harvey, citrusfruits vary in color, but variations from the standard varietal'color donot necessarily mean that the fruit is immature or of low quality. Thispatent discloses a method of enhancing the color of fruit by subjectingthe fruit to the action of a neutral or alkaline oleaginous materialcontaining a coloring agent and suggests further that at least part ofthis mixture is neutralized by a base. This produces a soap which inconjunction with the proper dye is used to treat off-color fruit. Thissolution due to its constituents is of necessity alkaline in nature. ThePatent No.

2,062,903 to James 0. Handy treats citrus fruit with an aquosolufacientwhich comprises a sodium salt of various compounds or a trlethanolaminesalt of a fatty acid.

These patents disclose methods for the treatment of citrus fruit whichin actual practice require temperatures much in excess of 120 F. forcoloring the orange satisfactorily-i. e. usually between 127 F. and 132F.with an oil soluble dye suspended in an alkaline aqueous bathcontaining an oil solvent for dye or containing a saponified oil bywhich the dye is dispersed in the solution, with or without added oilysolvent for the dye, so as to impregnate the skin or peel of the fruitwhen any dyeing of the fruit is contemplated. In such alkaline baths,unless great care is exercised to maintain the primary con-. centrationof solvent therein, when such solvent is used, and the properemulsiflcation of it, the fruit is burned and, where soap and dyes aloneare employed in such baths, very high temperatures in the order of 130to 140 F. are required.

The object of the present invention is to enhance the natural colorationof citrus fruit, parv ticularly oranges, by the use of a color bathwhich i does not employ a soap but in which the soap is replaced by asurface active agent of a catiomc type that suspends the dye in such astate of subdivision that its entrance into the peel is facilitated andaccomplished at considerably lower temperatures than those at presentemployed, thus retaining the flavor of the fruit; that provides a mediumwhich enhances the activity of a fungicidal agent for the fruit; thatmay be compounded with greater ease than known color baths; that may beused with water containing iron and other minerals without previouslybeing subjected to softening treatment; and that gives a suspension ofthe dye in the concentrated form that has better keeping qualities instorage, as respects suspension, for longer periods of time prior todilution for use than other known citrus fruit coloring concentrates.

These objects are attained broadly by use of an aqueous bath, containingcationic surface active agents and a suspension of a dyeing agent, andbringing the fruit into contact with such ath.

Surface active agents have several general uses, one of which is adispersion of a solid into a liquid to produce a suspensoid. Thesesurface active agents fall into three general classifications,hydrophilic, anionic and cationic. The cationic and anionic compoundsare usually long chain carbon compounds with a terminal grouping capableof ionizing when put into solution in an aqueous medium. When finelydivided material, which is to be dispersed, is placed or pro duced insuch an aqueous medium containing an ionized surface active agent, themolecules of the ionized surface active agent orient themselves so thatthe carbon chain of the molecules either dissolve in or are attracted bythe finely divided material to be dispersed, while the terminalgroupings bearing the charge of the molecules extend into the aqueousmedium. In this manner an aggregation of finely divided and stabilizedparticles are formed in the aqueous medium, each of which are stabilizedby one or more electric charges. The surface active agents used incarrying out the present invention are of the cationic type which offermany advantages over the other two types of surface active agents.

The hydrophilic surface agents with respect to their molecular structureare typified by a long carbon chain molecule which bear no electriccharge in solution while the anionic surface agents are also typified bya long carbon chain molecule which bears a negative charge when actingas an emulsifier or dispersing agent, such as a fatty acid. 011 theother hand, the cationic agents are typified by a long carbon chainmoleaeoaeoo 3 dine with a terminal nitrogen containing group which bearsa positive charge when acting as a stabilizer for an emulsion orsuspensoid. Such cationic surface active agents are represented by theorganic amines in their many forms.

In carrying out the present invention an or- 4 pure compound. Thesemixtures are satisfactory- The Sharples Chemical Company and Armour &Company are two corporations marketing such amines.

The following compounds have been tried and have given satisfactoryresults:-

Trade name or designationby Armour & Company as of 1945 amines, presentprimary AM-ll20 Air-1140 AM-1160 AMll8.5-B AM-ll80 AM-Coco-D Per centPer cent Per cent Per cent Per cent Per cent Octyl. C g Decyl C Dodec C90 4 47 Tetradecyl. C 4 9 90 18 HexadecyL. C 4 90 30 6 8 OctadecyL. Cir6 25 93 6 Octadecenyl C l 2 4 45 1 5 Ave. M01. \Vt 185 213 244 263 267M0 Primary amine by titration 97 97 97 97 97 97 Approx. melting point, C24 29 41 55 21 All were of the purified" grade (distilled).

ganic amine or an organic amine salt solution is mixed, with or withoutheating (heatng being used to accelerate solution), with an oil-solubledye to form a concentrate. This concentrate is further diluted withwater to make a bath for the treatment of citrus fruit, more inparticular, oranges. The amines which are contemplated for use in thisinvention must have one or more of the hydrogen atoms attached to theammonium nitrogen replaced by hydrocarbon radicals. The organic aminesalts that fall within the scope of this invention are the amine saltsformed from the amines as defined herein and an acid of a monobasicorganic or inorganic type. It has been found that not all of thecompounds falling within this class will work satisfactorily, but onlythose compounds wherein at least one of the hydrocarbon groups containsto carbon atoms. It should further be related that the secondary andtertiary amines should contain only one carbon chain of the type justspecified and that the second side grouping in the secondary amine andthe second and third side groups in the tertiary amine should contain asfew carbon atoms as possible. The description herein given should not beconstrued to mean that ring configurations must be absent since it hasbeen found that some compounds consisting of a long carbon chainmolecule, to which is molecularly and terminally attached a nitrogencontaining ring, are also effective as surface active agents. Such acompound is represented by l-hydroxy ethyl-Z-hepta decenyl glyoxalideneamine, known on the market as Cationic Amine 220, which consists of along aliphatic chain connected to a glyoxalidine ring and ismanufactured by Carbon and Carbide Chemical Corporation, New York city,New York.

Another example of the production of an amine, having the properties setforth above, is a condensation product obtained by reacting ethyleneoxide with a substituted amine having a side chain of between 10 to 20carbon atoms and 2 replaceable hydrogen atoms attached to the nitrogenatoms. This type of reaction is illustrated by the condensation productof N primary hexa decyl amine with ethylene oxide.

The acids used to form the amine salts are monobasic acids such ashydrochloric, hydrobromic, acetic, formic, lactic, etc.

It is well known that many commercial amines on the market are handledunder trade names and are sometimes a mixture of amines rather than aOne of the preferred materials is the amine prepared from abietic acidand the substance has the formula C20 Hal-NH:

Any one of the above amines or any mixture thereof may be employed. Inaddition to these compounds above noted, the compounds known asAlvi-ZiZU and AMCLr-4 COCO-C may be employed, the first compoundconsisting primarily of didodecyl ammonium chloride (secondary amine)and the second compound consisting of a mixture of quaternary ammoniumsalts containing an aliphatic side chain having 12 to 14 carbon atoms.The best results were obtained with AMCL-4 COCO-C, AM-Coco-B, AM-2120and the amine prepared from abietic acid; and also with Arquad-S,Arquad-T, Ethomeen S-20, Ethomeen 8-25 and compound RD1023 obtainablefrom Armour 81 Company. Arquad-S is a quaternary ammonium compoundhaving a side chain principally containing 18 carbon atoms; Arquad-T issimilar in structure having a side chain of 16 to 18 carbon atoms;HD1023 is a condensation of amines containing 16 to 18 carbon atom sidechains with ethylene oxide and the resulting amine formed into aquaternary salt; and the Ethomeens are amines containing a carbon chain0-16 to C-l8 in length which have been modified, by the addition ofethoxy and hydroxy substituents to the molecules, to increase the Watersolubility of the amine.

As one example or formula for preparing an amine salt dispersionaccording to the present invention, mix 1 pound of a dispersible edibleoilsoluble dye (preferably Food, Drug and Cosmetic-Red No. 32) and 18pounds of AM-Coco-B and heat, preferably with stirring, to obtain asuspension of the dye, the necessary amount of hydrochloric or aceticacid being added to neutralize the amine.

As an example of a formula using quaternary salt dispersion according tothis invention, mix 1 pound of dispersible edible oil soluble dye(preferably F. D, C. Red No. 32) and 18 pounds of RDlO23 and then heat,preferably with stirring, to obtain a suspension of the dye.

As an example of a formula for using an amine base according to thisinvention, mix 1 pound of dispersible edible oil soluble dye (preferablyF. D. C. Red No. 32) and 18 pounds of Ethomeen 3-25 and then heat,preferably with stirring to obtain a suspension of the dye.

asoaoos The above mixtures are 100% concentrates and may be shipped tocustomers or user and/or stored by him until used. This isadvantageousin that these 100% concentrates have less bulk and weightand remain in a liquid stateover concentrates using anionic dispersingagents and which have to be diluted with water to prevent theconcentrate from becoming a solid mass and difficult to handle by thecustomer; however, the

concentrates of the above formulae, in certain circumstances, may besold in slightly diluted form by the addition of small quantities ofwater (say 20 gallons to the above formula) so as to facilitate mixingin the bath by inexperienced personnel, but this is not ordinarilynecessary.

A concentrate, prepared as above, is formed into a bath by the additionof water diluting the concentrate to the extent that the finalconcentrate of dye will be approximately .025% in the total bath. Thisis about 1 part of dye to 4000 parts of water. The oranges are contactedwith said bath (by submerging and flooding or spraying) at'temperaturespreferably ranging in the order of 104 F. to 120 F. for the necessaryperiod of time (usually from 2 to 4 minutes) which gives a permanentsatisfactory color depending upon the condition of the fruit and uponthe depth of coloration desired. Excellent results have been obtainedwith a bath temperature between 110 F. and 118 F., to properly color anorange with a uniform color and free from blotches and of the maximumlegal intensity. The higher limit of the approximate range given abovemay be extended to the legal limit of 124 F. but it is to beaminocompounds may be used in the form of the free base and certainothers of them, being insoluble in water, must be used in the form ofthe salt. By the addition to these formulae of an amount of higheralcohols-having limited water solubility, such as terpineol, terpinol,methyl isobutyl carbinol, octyl alcohol, hexyl alcohol, amyl alcohol andbutyl alcohol as a few examplesmore dye may be added, when coloringcertain types of citrus fruit having a rind more resistant to thepenetration of the dye, as in the case of Valencia oranges as anexample. The addition of such alcohols assists in the suspension of thedye when the concentrate is diluted with water. The use of thesealcohols is not necessary to the carrying-out of the broad invention,but they may be used without harmful effects for the purpose juststated. Also, these alcohols act as anti-foaming agents.

The following examples of suitable formulae to incorporate the higheralcohols have been found to be:

Example I parts (by weight) alpha terplneol 10 parts (by weight) methyliso-butyl carbinol 4 parts (by weight) F. D. & 0., Red, No. 32

40 parts (by weight) Ethomeen 8-25 Example I! 10 parts dispersing agent1 part dye 3 to 10 parts pine oil (terpene alcohols) These concentratesare diluted about 1 to 400 with water to make a dye bath which can beused for coloring oranges. I the Example I above given, an optimumdispersion of the alcohol is produced so that an optically clear,cherry-red dispersion is obtained. When the lower molecular weightalcohols, such as butyl alcohol and amyl alcohol, are employed, a muchless dispersing agent is required than when the higher molecular weightalcohols are used. The proportion of alcohol to be used is dependent onthe amount of coloration desired to be imparted to the fruit and thespecific alcohol used-that is to say from 1 part or less to parts of thealcohol. Therefore, it is obvious that proportions of these alcohols maybe varied within wide limits, from the optimum above given, providedthat a stable condition of the bath is maintained. It has been foundthat as much as 90 parts of butyl alcohol or 30 parts of methyl butylcarbinol may be employed instead of the pine oil in the second examplegiven above. The emulsion becomes unstable, when its appearance ischaracterized by a cloudy, opaque, light orange color and when thealcohol has a tendency to separate out. This condition should be avoidedbecause, if the emulsion becomes unstable through the incompleteemulsification of the alcohol, there is danger of burning the fruit orunevenly coloring the fruit.

. Heretofore, in the enhancement of coloration of oranges, where bathsare used, in which the fruit is contacted by the bath, it has beennecessary to limit the alkalinity of this bath to a very narrow range,for instance in the order of pH's 7.5 to 11 with most baths maintainedat or approximately a pH of 8. It has been found, that with the cationicagents disclosed herein baths can be prepared having a pH varying from 4to 11. The extremes of this range have been tested and give verysatisfactory results. Therefore, because of these satisfactory results,it is felt that this range may be extended, if necessary, beyond theselimits and still give good deepening of the color in the skin of thefruit, while heretofore only a bath of limited pH could be used.Consequently, by reason of this invention the bath can be used at any pHwhich will allow the use of the naturally occurring water of an areawhere the invention is being practiced, without correction ormodification of this water, which correction has heretofore beennecessary.

Many advantages in the process herein disclosed are apparent to oneskilled in the art. A better suspension is obtained of the dye in anamine solution by the use of a water soluble amine wherein the dye is ina very fine state of sub-division known as a suspensoid" thus requiringthe use of smaller amounts of dye and more completely utilizing the dyethan do known soap alkaline and other bath solutions. It does not havethe disadvantages of an added excess of fatty acids or other oily orgreasy material used to carry the dye from a suspension to the fruitrind. It operates at a low temperature well within the legal limit togive a colored fruit that is satisfactory in every respect.

Another advantage of this process over existing processes is the greaterease for compounding this formula as compared tothose containing soapwherein the dye is dissolved in the fatty acid and the soap formed .byadding an alkali. This partial neutralization requires morecarefulcontrol than can be obtained in the average fruit treating plant.Therefore, it is the custom in the trade to ship the concentrate from acentral laboratory to the plant. The present process does not requirethe use of controls of this type and it is therefore possible to preparethe concentrate directly at the plant where it will be used to dye thefruit.

Another advantage resides in the absence of an oily solvent in the bathand the low temperature at which the dyeing process may take place.Previously, the use of higher temperature and/or an oily solvent haveresulted in the loss of flavor of the fruit, burning the fruit andcausing removal of a large part of the natural wax coating of citrusfruit. The present process, by the employment of a lower temperature andan amine bath and the elimination from the bath of oily or oil-likematerial, gives a coloring bath that does not burn the fruit andproduces a superior colored product which retains more of its nat-- uralflavor. If desired, the fruit may be artificlally waxed by known methodsto give a high lustre and provide shrinkage control of the fruit.

Still another advantage of this process over existing processes is thefact that water containing iron or other dissolved mineral matter, suchas hardwater found in those communities where limestone or coralformations are common, may

be used directly without a, preliminary treatment.-

The alkaline earth and metallic elements remain in solution rather thanprecipitate out as soaps. Particularly in soap baths, these precipitateseventually foul the dye bath and render it inoperative.

Having thus fully set forth my invention in a manner as will enableothers skilled in the art to use and compound the same and, as an aidthereto, having set forth the composition of the compounds that are nowpurchasable under trade names, I claim:

1. In a process of enhancing the varietal color of citrus fruit, thestep of bringing the fruit into contact with a dye suspended in asolution of an amine at a temperature in the order of 104 F. to 124 F.,said amine having at least one hydrocarbon chain of to 20 carbon atoms.2. In a process of enhancing the varietal color of citrus fruit, thestep of bringing the fruit into contact with an edible oil soluble dyesuspension in an aqueous bath of an aliphatic substituted amine cationicsurface active agent having at least 1 hydrocarbon chain of 10 to 20carbon atoms, said bath being at a temperature approximately 104 F. to124 F.

3. In a process for enhancing the varietal color of citrus fruit, thestep of bringing the fruit into contact with a dye suspended in asolution of a l-hydroxy ethyl-Z-hepta decenyl glyoxalidene amine, saidsolution being at a temperature approximately 104 F. to 124 F.

4. In a process of enhancing the varietal color of citrus fruit, thestep of bringing the fruit into contact with a dye suspended in asolution of a cationic amine at a temperatureapproximately 104 F. to 124F., said amine having at least one hydrocarbon chain of 10 to 20 carbonatoms and which amine is modified by the addition of ethoxy and hydroxygroups.

5. In a process of enhancing the varietal color of citrus fruit, thestep of bringing the fruit into contact with a dye suspended in asolution of a cationic amine at a temperature approximately 104 F. to124 F., said amine having at least one hydrocarbon chain of 10 to 20carbon atoms and which amine is modified by the addition of ethoxygroups.

6. In a process of enhancing the varietal color of citrus fruit, thestep of bringing the fruit into contact with a dye suspended in asolution of a cationic amine at a temperature approximately 104 F. to124 F., said amine having at least one hydrocarbon chain of 10 to 20carbon atoms and which amine is modified by the addition of hy- Qdroxygroups.

7. In a process of enhancing the varietal color of citrus fruit, thestep of bringing the fruit into contact with a dye suspended in asolution of a cationic amine at a temperature approximately 104 F. to124 F., said amine having at least one hydrocarbon chain attached to aglyoxalidine ring.

8. In a process of enhancing the varietal color of citrus fruit, thestep of bringing the fruit into contact with an edible oil soluble dyesuspension in an aqueous bath of an aliphatic substituted cationic aminesurface active agent having at least 1 hydrocarbon chain of 10 to 20carbon atoms and containing at least one higher alcohol having a limitedwater solubility, said bath being at a temperature approximately 104 F.to 124 F.

9. In a process of enhancing the varietal color of citrus fruit, thestep of bringing the fruit into contact with 1 part of an edible oilsoluble dye suspension in an aqueous bath of 10 parts of an aliphaticsubstituted cationic amine surface active agent having at least 1hydrocarbon chain of 10 to 20 carbon atoms and containing 3 to 10 partsof terpene alcohol, the bath being at approximately 104 F. to 124 F.

10. In a process of enhancing the varietal color of citrus fruit, thestep of bringing the fruit into contact with 1 part of an edible oilsoluble dye suspension in an aqueous bath of 10 parts of an aliphaticsubstituted cationic amine surface active agent having at least 1hydrocarbon chain of 10 to 20 carbon atoms and containing up to aboutparts of a higher alcohol having a limited water solubility, the bathbeing at approximately 104 F. to 124 F.

11. A bath for enhancing the varietal color of citrus fruit, containingan edible oil soluble dye and a substituted cationic amine having atleast one hydrocarbon chain of 10 to 20 carbon atoms.

CARL E. GERICKE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,970,578 Schoeller et al Aug.21, 1934 2,049,563 Harvey et 'al Aug. 5, 1936 2,092,091 Sharma Sept. 7,937

FOREIGN PATENTS Number Country Date 407,973 Great Britain of 1934

1. IN A PROCCESS OF ENHANCING THE VARIETAL COLOR OF CITRUS FRUIT, THESTEP OF BRINGING THE FRUIT INTO CONTACT WITH A DYE SUSPENDED IN ASOLUTION OF AN AMINE AT A TEMPERATURE IN THE ORDER OF 104*F. TO 124*F.,SID AMINE HAVING AT LEAST ONE HYDROCARBON CHAIN OF 10 TO 20 CARBONATOMS.